I. Field of the Invention
The present invention relates generally to linear actuators. More particularly, the present invention relates to an apparatus for linearly displacing an output member in the form of a mechanical control wire, by means of at least two wire-gripping assemblies operating in concert with an intermediate compressible assembly provided therebetween. The wire is gripped by means of two one-way linear clutches setable in either direction. The clutches are mounted on opposite ends of the compressible assembly. The intermediate assembly is contracted by an array of shape memory alloy wires, then allowed to expand thereby pulling tendon wire therethrough.
II. Description of the Relevant Art
It is often desired to apply linear motion to an output member such as a mechanical control wire in order to displace the member to an accurate position.
The rack-and-pinion assembly, the jack screw and the hydraulic cylinder assembly are the preferred and known mechanisms presently used that are able to generate linear motion. Each of these mechanisms has its own special attraction to a given application.
However, while none of these mechanisms is complicated in theory, resulting linear motion actuators themselves are relatively complicated in practice, and usually include expensive and heavy elements such as carefully machined gear and shaft members. Others require expensive, complicated and massive support systems.
Regardless of their cost, complexity and size the known linear actuators systems serve well their specific functions. However, they fail to effectively function in other linear motion areas. For example, in the art of robotics comprising robotic arms, fingers and the like, the required motions are articulate and the required mechanism is light. Motion multiplexing from a single central actuator reduces the multiple duplication of motor weights and equipment costs. In this application, delicate, strong, fast, and accurately controllable movement of one or more control wires is critical. An improved analog for muscles and tendons in robots is wanting.
The known methods of linear actuation fail to meet the very specific and, in their own way, very demanding needs of robotics. Accordingly, prior approaches to providing linear actuators to robot control machines have been assemblages of parts from other technologies, neither being a perfect fit nor a perfect function.